The most common antenna for beam steering or direction finding is a phased-array antenna, in which a phase shifter is used to alter the input phase at each radiating element. Since the cost of each phase shifter is very high, such a prior art phased-array antenna becomes expensive especially when a large number of elements are needed for a high-gain application.
A phased-array antenna steers the beam when used as a transmitter while the antenna as a receiver receives signals as the antenna points to the direction of the incoming signal. The transmitting antenna is identical to the receiving antenna according to the reciprocity theorem.
As will be apparent, such a prior art antenna array with M×N elements requires M×N phase shifters. A need therefore exists for a reduction in the number of phase shifters required to accomplish beam steering. This need is especially critical in antennas using printed circuit stripline technology where phase shifters are very expensive compared to the cost of an antenna array radiating element.